.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.\" Copyright (c) 2019 Edward Tomasz Napierala <trasz@FreeBSD.org>
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.Dd September 18, 2025
.Dt CDCEEM 4
.Os
.Sh NAME
.Nm cdceem
.Nd USB Communication Device Class Ethernet Emulation Model driver
.Sh SYNOPSIS
To compile this driver into the kernel,
place the following lines in your
kernel configuration file:
.Bd -ragged -offset indent
.Cd "device uhci"
.Cd "device ohci"
.Cd "device usb"
.Cd "device miibus"
.Cd "device uether"
.Cd "device cdceem"
.Ed
.Pp
Alternatively, to load the driver as a
module at boot time, place the following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
if_cdceem_load="YES"
.Ed
.Sh DESCRIPTION
The
.Nm
driver provides support for USB devices based on the USB Communication
Device Class Ethernet Emulation Model (CDC EEM) specification.
.Pp
The driver works on both host, and device-side; see
.Xr usb_template 4
for details.
.Pp
The USB device appears as a regular network interface on both sides,
transporting Ethernet frames.
.Pp
For more information on configuring this device, see
.Xr ifconfig 8 .
.Pp
The
.Nm
driver does not support different media types or options.
.Sh SYSCTL VARIABLES
The following variables are available as both
.Xr sysctl 8
variables and
.Xr loader 8
tunables:
.Bl -tag -width indent
.It Va hw.usb.cdceem.debug
Verbosity level for log messages from the
.Nm
driver.
Set to 0 to disable logging or 1 to warn about potential problems.
Larger values enable debugging output.
Defaults to 1.
.It Va hw.usb.cdceem.send_echoes
If set to 1, the driver will send an Echo EEM packet when the
interface is brought up.
While responding to Echo is mandatory, some devices cannot handle it.
Only use for debugging.
Defaults to 0.
.It Va hw.usb.cdceem.send_fake_crc
If set to 1, the driver will use 0xdeadbeef as the CRC value
for outgoing Data EEM packets.
Only use for debugging.
Defaults to 0.
.El
.Sh SEE ALSO
.Xr arp 4 ,
.Xr cdce 4 ,
.Xr intro 4 ,
.Xr ipheth 4 ,
.Xr netintro 4 ,
.Xr urndis 4 ,
.Xr usb 4 ,
.Xr usb_template 4 ,
.Xr ifconfig 8
.Rs
.%T "Universal Serial Bus Communications Class Subclass Specification for Ethernet Emulation Model Devices"
.%U https://usb.org/sites/default/files/CDC_EEM10.pdf
.Re
.Sh HISTORY
The
.Nm
device driver first appeared in
.Fx 12.1 .
.Sh AUTHORS
The
.Nm
driver was written by
.An Edward Tomasz Napierala Aq Mt trasz@FreeBSD.org
under sponsorship from Hewlett Packard Enterprise.
